JPH08289347A - Device that couples antenna with wrist-portable selective call receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an antenna to be easily attached to and detached from the wrist of a user by coupling the antenna in a strap which can be put in and removed from a wrist watch type case with pins to a receiver in the case by using a capacitor formed of two plates. SOLUTION: A selective calling receiver 10, such as the pager, etc., is constituted by supporting a receiver circuit 12 in a wrist watch type plastic case 14 and surrounding the circuit 12 with the case 14 and a cover 16. The end section 13 of a strap 18 which is resemble to a wrist strap is attached to the facing side faces 15 and 17 of the case 14 in a state where the section 13 can be detached form the side faces 15 and 17 and can rotate so that the receiver 10 may be attached easily to the wrist of a user. A coupling device 11 is composed of a capacitor 50 composed of a plate 22 connected to the circuit 12 through a conductor 28 and a plate 26 electrically connected to a flexible antenna 24 in the strap 18 at one end 25. Therefore, the receiver 10 and strap 18 can be attached, detached, and exchanged easily by coupling the signal from the antenna 24 with the circuit 12, namely, the receiver 10 by means of the coupling device.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates generally to the field of wireless communications, and more particularly to the antenna coupling of a handheld selective call receiver.

[0002]

2. Description of the Prior Art Selective call receivers or pagers having an antenna mounted in a wristwatch sized case and carried by a wristwatch band are well known. The wristwatch has a conventional barrel pin with an extension with a spring.
Or, it is usually removably connected to a band or strap by a removable pin, such as a roll pin. Once connected, the strap and watch are pivotable about each other. But, unfortunately,
Known watch-sized pagers are connected to known watch-type bands that carry an antenna by a device that is substantially different from the device in which the watch is normally connected to the watch band. The antenna carried by the known wristwatch band is electrically coupled by a direct mechanical connection to a selective call receiver in a known wristwatch-sized case.
As a result, the joint between the case and the band or strap is undesirably strong and inflexible, and the case and band cannot pivot about each other. Furthermore, the antennas used with known wrist-worn pagers have the inconvenience that it is necessary to break the antenna connection when removing the old band and make the antenna connection when wearing the new band. Because of this, it cannot be easily replaced. Precious metal merchants who know only conventional watches and bands cannot easily replace the bands on known prior art wristwatch pagers without special training and equipment. An example of a watch size pager with such non-standard connections is U.S. Pat. No. 5,17, issued to Matsui on January 12, 1993.
No. 9,733.

In some known wrist-worn pagers, the band is changed because a mechanical connection that electrically couples the antenna and receiver is added to another mechanical connection that secures the case to the band. This has the inconvenience of requiring two different actions. Examples of such wrist-worn pagers are U.S. Pat. Nos. 4,754,285 and 198 issued to Robitaille on June 28, 1988.
U.S. Pat. No. 4,764 issued to Dickey on September 6, 8
No. 9,656.

Other known wrist-worn pagers have the inconvenience of having a mechanical connection between the antenna and a band pin for electrically coupling the antenna to the pager. Such direct electrical connections do not allow the pins to be removable and require a special pin to attach the band to the case. An example of such a wrist-worn pager is U.S. Pat. Nos. 3,032,651 and 1, issued to Gisiger-Stahli et al. On May 1, 1962.
Shown in US Pat. No. 5,159,713 issued October 27, 992 to Gaskill et al.

An example of a prior art wristwatch pager that uses a spring-loaded pin to mechanically secure the band to the case was given to MacNak et al. On March 28, 1989 and assigned to the assignee of the present invention. U.S. Pat. No. 4,811
No. 7,196. However, MacNak et al. Do not disclose capacitive coupling to the antenna receiver. Furthermore, MacNak et al. Do not disclose the spring-loaded pins involved in electrically coupling the antenna to the receiver.

An example of electrically coupling a wristwatch pager to an antenna using a mechanical connection is February 23, 1993.
Shown in US Pat. No. 5,189,431, assigned to Marinelli on the date and assigned to the assignee of the present invention. Marine
lli's method provides satisfactory performance under most, but not all, operating environments. But Marine
Lli's method relies on a concave semi-circular arcuate contact that is always in contact with a convex semi-circular arcuate contact and is subject to dust between the convex and concave contacts. In addition, wiping between the concave semi-circular arc contact on the pager and the convex semi-circular arc contact on the band causes unwanted friction.

A cordless telephone that capacitively couples an antenna within a rigid hinged element to a radio telephone within the body was assigned to Krenz et al. On Dec. 8, 1992 and assigned to the assignee of the present invention. US Pat. No. 5,170,1
No. 73. However, Krenz et al. Disclose a capacitor co-located with and in the hinge.

Therefore, there is a need for a device that electrically couples an antenna carried by a removable wristwatch band or strap to a selective call receiver mounted on a wristwatch case, yet overcomes the above-mentioned drawbacks of the prior art. Is.

[0009]

One aspect of the present invention is an apparatus that facilitates wearing a selective call receiver on a wrist. The selective call receiver is supported by the case. This device
It has a strap rotatably connected to the case to secure the case to the wrist, and an antenna carried by the strap. The device comprises a capacitor having a first plate and a second plate spaced apart by a preselected distance.
The first plate is fixed on the case and electrically coupled to the selective call receiver. The second plate is fixed to the strap and electrically coupled to the antenna. This device
Furthermore, it is constituted by means for pivoting the strap with respect to the case, away from the first plate. The device further comprises means for maintaining a preselected distance between the first plate and the second plate while pivoting the strap away from the second plate with respect to the case.

Another aspect of the present invention is a selective call receiver. The selective call receiver includes a receiver circuit and a case that holds the receiver circuit. 1 in the case
There are pairs of mounts, and at least one mount is electrically coupled to the receiver circuit. The selective call receiver is further configured with at least one long strap that secures the case to the user, the strap having two sides with a diameter and a shaft, and a lateral hollow extending between the two sides. It has a cylindrical opening. The selective call receiver is further constituted by a shielded metal cylinder having a diameter larger than the diameter of the opening, the cylinder being coaxially embedded in at least one strap. The antenna is held by at least one strap and is electrically coupled to the barrel. The selective call receiver further comprises a cylindrical metal pin having a diameter approximately the same as the diameter of the opening, the pin being removably mounted on a pair of mounts and electrically coupled to the at least one mount. A connection is formed and is removably coaxially disposed within the opening to capacitively interact with the barrel.

Yet another aspect of the present invention is an apparatus for coupling an antenna supported by an insulating material to a selective call receiver supported by a case. The insulating material is pivotally attached to the case by two hinges. This device is constituted by a capacitor located between the two hinges. The capacitor has a first plate located on the case and a second plate located on the insulating material. The device is further constituted by means for maintaining the capacitance of the capacitor substantially constant during swirling of the insulating material with respect to the case.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a selective call receiver 10 such as a pager is shown mounted in a wristwatch case 14, preferably made of plastic. Selective call receiver 10
The operation of is well known to those skilled in the art. Selective call receiver 10
Is constituted by the receiver circuit 12 supported by the case 14. The selective call receiver 10 is surrounded by a case 14 and a cover 16. A strap 18 having at least one end 13 is used to facilitate wearing the selective call receiver 10 on a user's wrist. At least one end 13 of the strap 18 preferably resembles the end of a standard watch band. Each of the at least one end 13 of the strap 18 is
The case 14 is rotatably connected to the facing side surfaces 15 and 17 of the case 14 in a detachable manner.

The device 11 for coupling the antenna to the selective call receiver 10 is constituted by a capacitor 50 having two capacitance plates, which are separated by a preselected distance 51 (FIG. 2). The first plate 22 and the second plate 26 are separated from each other. The case 14 has at least one of the opposite side surfaces 15 and 17.
And a substantially arcuate recessed recess 20 that overlies the first plate 22 and receives the first plate 22. As shown in FIG.
The first plate 22 has a shaft 23, a length 31, L, and a radius 3
5, R and an arcuate portion of a cylinder having angular dimensions 63, α. Referring again to FIG. 1, the first plate 22 is mounted within the substantially arcuate concave recess 20 and forms the concave portion of the outer surface of the case 14 at one of the opposing sides 15. Alternatively, as shown in FIG. 2, the first plate 22 is embedded in the case 14 at a distance 55 on one of the opposite sides 15 by a plastic molding method well known to those skilled in the art. The first plate 22 is electrically connected by connecting the conductor 28 to the receiver circuit 12.

The strap 18 is preferably flexible and
Made of plastic or injection moldable insulating material. The strap 18 is elongated and has two sides 19, 21. The strap 18 has an axis 29 and has a transverse hollow cylindrical opening 30 extending between the sides at at least one end 13. An antenna 24, which is preferably a flexible antenna, is located within the strap 18. The antenna 24 is preferably a thin, flat, elongated strip as shown in FIG. Alternatively, the antenna is a wire. The antenna 24 is electrically connected to the second plate 26 at one end 25. Second plate 2
6 is arranged coaxially with the lateral hollow cylindrical opening 30 and entirely within the material of the strap 18. The antenna 24 is embedded in the strap 18 and the opening 30 is formed by the insertion molding method.
The operation of forming is well known to those skilled in the art. Therefore, FIG.
The distance 49 shown at is obtained between the second plate 26 and the outer surface 48 of the strap 18.

The second plate 26 has a shaft, lengths 31, L,
It is an arcuate portion of a cylinder having a radius of 37, r and an angular dimension of 65, β. However, β is substantially larger than α, but 2
Less than 70 degrees. Alternatively, the angular dimensions 65 and β of the second plate 26 are substantially smaller than the angular dimension α of the first plate 22. In each case, in the preferred embodiment, the first plate 22 and the second plate 26 each have a cylindrical (not shown other than arcuate) arcuate portion 3.
9, 41, each arcuate portion containing substantially different frequencies.

The strap 18 is attached to the case 14 using a pin 32, which is preferably a compressible watch spring pin that is slip fit within the opening 30 of the strap 18. It is convenient for the pin 32 to be of a type that the noble metal quotient is familiar with and therefore can be removed by conventional methods. In fact, the strap 18 can be removed like a standard watch band without an antenna. The material of the strap 18 isolates the second plate 26 from the pin 32. The pin 32 comprises a barrel portion 34 having a diameter and has extensions 36, 38 having a diameter smaller than the diameter of the barrel portion. Extension 3
Plain bearings are formed between the barrel portions 34 and 6 and 38, respectively, so that the barrel portion 34 can be rolled with respect to the extension portion.

The opposite sides 15, 17 of the case 14 each have a pair of mounts 56, 57 and 58, 59, respectively, which project from the outer surface 48 of the case and are preferably continuous with the material of the case. Made of materials that The mounts 56 to 59 are separated from the first plate 22 and the second plate 26. Since each of the facing sides 15, 17 of the case 14 is substantially similar, only one of the facing sides 15 will be described in detail. The mounts 56 and 57 have cavities 60 and 61.
One cavity 60 on one mount 56 opposes the other cavity 61 on the other mount 57. The cavities 60 and 61 are sized to hold the extension portions 36 and 38 of the pin 32 tightly. The cavities 60 and 61 are the case 14
It is in the material of. Therefore, the pin 32 is connected to the receiver circuit 1
2 and also from all other electrical components of the selective call receiver 10. The cavities 60, 61 are located on the case 14 at a predetermined distance 45 from the outer surface of the case, and when the strap is attached to the case by the pins 32, at least one end 13 of the strap 18 rotates around the case. be able to. The cavities 60,61 on the mounts 56,57 cooperate with the extensions 36,38 of the pin 32 to form two hinges. When the strap 18 is connected to the case 14, the axis of the second plate 26 becomes coaxial with the axis 23 of the first plate 22. The strap 18 can swivel around the case 14. Strap 1
During the turning of 8, the shaft of the first plate 22 and the second plate 2
The axis 23 of 6 remains coaxial. Moreover, the strap 18 remains at a constant distance 53 from the case 14 during pivoting, which has the advantage that the device 11 is relatively insensitive to friction as compared to prior art coupling devices.

The capacitive engagement of the first plate 22 with the second plate 26 electrically couples the antenna 24 to the selective call receiver 10. The fixed distance 53 is chosen to allow capacitive coupling between the first plate 22 and the second plate 26 at the operating frequency of the selective call receiver.
It is necessary to maintain a preselected distance 51 between the first plate 22 and the second plate 26, ie a fixed distance 53 in order to maintain a constant capacity. During turning, the first plate 22 and the second plate 26
Means for maintaining the preselected distance 51 between the pin 32 and the barrel portion 34 of the pin 32 and the strap 18 include a sliding fit between the extension portions 36, 38 of the pin 32 and the cavity 6.
A slip fit between 0 and 61 is included.

FIG. 2 is an enlarged side view of a portion of case 14 and a portion of strap 18 of FIG.
The plate 22 is shown embedded at a distance 55 within the case, rather than the outer surface 44 of the case. Preferably, the distance 55 is about 0.5 mm. The capacitor 50 includes the first plate 22, the material of the case 14, the void 4
6, the material of the strap 18 and the second plate 26.

Referring to FIG. 2, the capacitance C of the capacitor 50
Is described by the following equation:

[0021]

[Equation 1] Where ε ₀ is the permittivity of free space, ε ₁ is the permittivity of the material of the case 14, ε ₂ is the permittivity of air, and ε ₃ is the permittivity of the strap 18. α is generally the smaller angular dimension of the first plate 22 and the second plate 26, but in the preferred embodiment α is the first plate 2.
2 corner dimensions. L is the length of the second plate 22 and the second plate 26. R and 35 are the radius of the arc of the first plate 22, and r and 37 are the radius of the arc of the second plate 26. y is the outer surface 44 of the case 14 and the strap 1
8 is the radius of the annular segment of the void 46 between the outer surface 48 and x, and x is the radius of the annular segment of the strap material portion between the second plate and the outer surface of the strap. The material portion of the strap 18 between the second plate 26 and the outer surface 48 of the strap acts as a dielectric. Equation (1) is used to calculate the capacitance C of the capacitor 50 in the preferred embodiment with three different materials between the two capacitance plates of the capacitor, namely the material of the case 14, the material of the air gap 46 and the material of the strap 18. Used. The capacitor 50 is equivalent to three capacitors connected in series. That contributes casing 14 material in the capacitor C _1, voids 46 contribute to the capacitance C _2, the capacitor C ₃ strap 18 material contributes. Therefore, the total capacity is C = 1
It becomes / C ₁ + 1 / C ₂ + 1 / C ₃ . The capacitance value varies depending on the selected dielectric material, plate dimensions and plate spacing. For example, the relative permittivity is ε ₁ = 5.1, ε ₂ = 1,
ε ₃ = 9, ε ₀ = 8.85 x 10 ^-12 farads / meter; plate dimensions L = 12.7 mm, α = 135 degrees, R =
2.4 mm, r = 1.4 mm; annular segment x = 0.
4 mm; Equation (1) with an annular segment y = 0.1 mm gives a capacitance C of 2.1 pF. 2.1 pF
Is relatively low due to the relatively large preselected distance 51 between the first plate 22 and the second plate 26 (1.0 mm). As a result, the device 11 with the above dimensions is very efficient at operating frequencies of selective call receivers above 130 MHz.

Alternatively, the first plate 22 may be attached to the case 14
Mounted on the outer surface 44 of the second plate 26 and embedded in the strap 18. The capacity C of this first alternative is determined as follows:

[0023]

[Equation 2] Dielectric constants ε ₂ = 1, ε ₃ = 9, ε ₀ = 8.85 x 10 ^-12 farads / meter; plate dimensions α = 180 degrees, L = 1
4.3 mm, R = 1.8 mm, r = 1.4 mm; annular segment x = 0.3 mm; annular segment y = 0.1 m
Equation (2) for C for m gives a capacitance of 5.1 pF. This first alternative has been found to work for all frequencies currently assigned by the Federal Communications Commission (FCC) for paging systems.

In a second alternative, not shown, the first
The plate 22 is embedded in the case 14 and the second plate 26 is on the outer surface 48 of the strap 18. In the second alternative, the second plate 26 forms a protrusion on the outer surface 48 of the strap 18. The capacity of the second alternative is determined by equation (3) for C as follows:

[0025]

(Equation 3) The second alternative has also been found to be valid for all frequencies currently assigned by the FCC for paging systems.

In a third alternative, not shown, the first
The plate 22 is on the outer surface 44 of the case 14,
The plate 26 is on the outer surface 48 of the strap 18.
The capacity of the third alternative is determined by equation (4) as follows:

[0027]

[Equation 4] In the third alternative, the capacity is limited because there is no dielectric other than air between the capacitive plates; therefore, the third alternative is preferably used at operating frequencies above 130 MHz.

The present invention includes an antenna 24 to a receiver circuit 12
Since capacitive coupling is used to transfer electrical energy to
The present invention is less susceptible to dust between the strap 18 and the case 14 as compared to prior art coupling devices that use conductive coupling.

Referring to FIG. 3, the strap 18 is pin 3
In order to further maintain the substantially constant capacitance of the capacitor 50 while swirling or rotating about 2, the selective call receiver 10 causes the strap to swivel with respect to the case 14 at a preselected frequency of 27, θ or more. It also has a means to restrict it from becoming. However, θ is β minus α. The preselected frequency θ is determined by the first plate 22
Is substantially equal to the angular dimension of the second plate 26. The strap 18 is attached to the case 14 so that the air gap between the first plate 22 and the second plate 26 is angularly equal to α even at the final limit of rotation. By limiting the rotation to θ degrees, the capacitance of the capacitor 50 is calculated using the angular dimension of only the smaller of the first plate 22 and the second plate 26. The means for limiting the pivoting of the strap 18 with respect to the case 14 includes edges 62 of the cover 16 and the case 1.
4 inside corners 64 are included. In FIG. 3, strap 18 is shown rotated about pin 32 in one direction up to a maximum angular distance. Movement in one direction is limited to a swing limit 87 by the edge 62 of the cover 16.
With reference to FIG. 4, the strap 18 is shown rotated about the pin 32 in another direction up to a maximum angular distance. To move in the other direction, move the inner corner 64 of the case 14
It is limited to another turning limit 89.

Referring to FIG. 5, a selective call receiver 10 is illustrated in an alternative embodiment of the present invention. According to an alternative embodiment of the present invention, the selective call receiver 10 comprises a receiver circuit 12 of conventional design surrounded by a case 70 and a smaller cover 71. The strap 18 is attached to the case 70 by a pin 32 that is press fit into the lateral hollow cylindrical opening 30 of the strap. Strap 1
8 can swivel around the case 70. By tightly press fitting between the barrel portion 34 of the pin 32 and the strap 18, the barrel portion and the strap rotate together without any relative movement while the strap pivots around the case. Barrel part 34 and extension part 3 of the pin
Plain bearings between 6 and 38 create a constant electrical connection between the respective extension and the barrel.

FIG. 6 shows a top view of an alternative embodiment of the present invention. The device 11 is shown here with a portion of the material of the strap 18 cut away to represent a shielded metal cylinder 86 which functions as one of the two capacitive plates. The strap 18 preferably comprises at least one flexible elongate wrist strap 43 that secures the case 70 to the user. The strap 18 comprises a transverse hollow cylindrical opening 30 having a diameter 83, a length 84 and an axis 85. Referring to FIGS. 5 and 6, the case 70 has at least 2
Has one side and has a continuous protrusion of case material on at least one side, which has a pair of mounts 7
8, 69 are formed. The mounts 78 and 69 have cavities 72 and 73 facing each other. Cavities 72,7
A metal bracket 7 that holds the end of at least one of the extensions 36, 38 of the pin 32 in at least one of the cavities 3 and forms an electrical connection with the pin 32.
4 is inserted tightly. The receiver circuit 12 is electrically connected to the metal bracket 74 by a bracket connecting wire 75. The extensions 36, 38 obtain a contact force against the arm 76 of the metal bracket 74 from the spring load supplied inside the pin 32. The use of the metal bracket 74 in each of the cavities 72 and 73 has an advantage that the adhesion strength of the strap 18 to the case 70 is increased. In an alternative embodiment, the capacitor 5
Zero is formed by the material of the interrupted metal cylinder 86, the barrel 34 that functions as the other of the two capacitive plates, and the strap 18 that functions as a dielectric. The selective call receiver signal is transmitted from the antenna 24 to the capacitor 50.
Coupled to the receiver circuit 12 via. With reference to FIG. 7, the interrupted metal cylinder 86 has a diameter 52 that is larger than the diameter of the transverse hollow cylindrical opening 30. Pin 32
Is preferably a metal cylindrical pin having a diameter 88, such as a conventional compressible timepiece spring pin. The diameter 88 of the pin 32 is approximately the diameter 83 of the transverse hollow cylindrical opening 30. Pin 32 is strap 18
The space 54 between the pin and the strap is negligibly small because it is slip-fitted into the opening 30 of the. Space 54
The dimensions are greatly exaggerated in FIG. 7 for clarity of illustration. The sliding fit between the pin 32 and the strap 18 prevents the accumulation of dust in the space 54,
Moreover, the pin can be removed using the conventional technique of a precious metal quotient. Preferably, the metal cylindrical portion 86 is blocked
Substantially surrounds the pin 32. Alternatively, the interrupted metal cylinder 86 has an elongated opening 90 such that the interrupted metal cylinder only partially surrounds the pin 32. The extension portions 36 and 38 connect the strap 18 to the case 70.
It becomes a means to turn about. Since both capacitance plates of the alternate embodiment capacitor 50 rotate together without any relative movement during the pivoting of the strap 18, the alternate embodiment requires a means to limit the pivoting of the strap. There is an advantage of not doing it. Therefore, the smaller cover 71 is smaller than the cover 16 because the edge 62 (FIG. 2) is not required to limit the swivel in one direction. Of course, it is not necessary to limit the other turn in alternative embodiments. Equation (4) is used to calculate the capacity of the alternative embodiment shown in FIGS.

The capacitance value required for coupling is determined by the following items: operating frequency of the selective call receiver, antenna type, case material, strap material and capacitive plate geometry. The dependence on frequency is unconditional, as many of the parameters for case and strap materials change with frequency. At frequencies around 40 MHz, the electrical properties of plastic materials are more favorable than those at frequencies around 900 MHz. This is because the material loss increases, and the relative dielectric constant of many plastics decreases as the frequency increases, which decreases the capacitance of the capacitor 50. Therefore, the third alternative of the embodiment shown in FIGS. 1 and 2 with the capacitive plate on the outer surface is preferably used at higher frequencies. The dimensions and spacing of the plates are adjusted so that capacitor 50 has negligible reactance at the operating frequency of the selective call receiver.

Depending on the type of antenna and the operating frequency, the capacitance C of the capacitor 50 is sufficient to resonate the antenna. The antenna used in many wrist-carrying selective call receivers is a loop antenna that is electrically small relative to wavelength. Since the loop antenna is inductive, capacitive tuning is used. The type of antenna has a great influence on the capacitance required in the device 11 for antenna resonance. Alternatively, a dipole antenna is used. Dipole antennas are also electrically small, but unlike loop antennas, dipole antennas are capacitive in nature. Therefore, inductive loads are used to employ capacitive tuning. Dipole antennas are designed to use a capacitance of 1-10 pF for antenna resonance. At lower VHF frequencies, multi-turn loop antennas wound around ferrite rods are typically used. A capacitance of 2-10 pF with respect to capacitor 50 is acceptable due to resonance, depending on the antenna size.
The effectiveness of ferrites decreases with increasing frequency. Moreover, over-winding of the multi-turn loop antenna at UHF frequencies can cause excessive inductance, which results in very low capacitance values for resonance. Therefore, ferrite is not used and the number of turns in the loop is reduced at UHF frequencies. At UHF frequencies, capacities of 1-10 pF are acceptable depending on the size of the antenna. High UHF frequency and low GHz
At frequency, a small single turn loop antenna and 0.
Capacities of 5-10 pF are used depending on the size of the antenna.

When the reactance becomes zero, resonance of the antenna is achieved. The reactance component of the small loop antenna is constructed as an inductor with a self-inductance L connected in series with the capacitor 50. Therefore, in the resonance state, the capacitance of the capacitor 50 is C = 1 / ω ² L
Is. Self-inductance L of circular loop of wire
Is given by equation (5):

[0035]

(Equation 5) Where μ is the wire transmittance, μ ₀ is the free space transmittance,
a is the radius of the wire used for the loop antenna, and b is the radius of the loop. If the wire radius is 1.6 mm and the loop radius is 3.2 cm, the self-inductance L
Is about 0.1614 μH. Therefore, the capacitance C = 5.1 pF produced by the device 11 shown in FIG. 1 is sufficient to obtain resonance.

FIG. 8 is a circuit diagram of an antenna 24 having impedance matching and resonant components. The antenna 24 shown in FIG. 8 is a single turn loop antenna for simplicity of illustration.
Use as an antenna. As previously mentioned, the antenna 24 in the strap 18 is inductive and capacitively tuned at the operating frequency of the selective call receiver. At resonance, the impedance seen by the input circuit configuration of the receiver circuit 12 is
Purely resistive, about 146.04Ω with copper wire
Becomes If the input circuit configuration of the receiver circuit 12 is somewhat inductive, then a coupling capacitor (coupling capacitor) 80 and a shunt capacitor (shunt capacitor) 82 are used to reduce the impedance of the combined circuit from the antenna 24 to the device 11. , The impedance of the input circuit configuration is conjugated and matched. For example, the impedance (146.04Ω) of the combined circuit from the antenna 24 to the device 11 is 50 + j90.
The coupling capacitor 80 is preferably 40.4 pF and the shunt capacitor 82 is preferably 8.7 pF to match the input circuit configuration impedance of The coupling capacitor 80 and the shunt capacitor 82 are mainly used in the receiver circuit 12
It is used to match the impedance of the input circuit configuration, and its effect on antenna resonance is small.

FIG. 8 shows opposite sides 15 of the case 14,
17 device 11 is shown. One side 15 opposite the case 14
Then, the capacitor 50 operates to resonate the antenna 24 at the operating frequency of the selective call receiver. Case 1
On the other side 17 of 4, the present invention couples the other end of the antenna 24 to ground in the receiver circuit 12 through another capacitor 40. It is not necessary to use the invention on both sides 15, 17 of the case 14. Of course, if the antenna 24 is a dipole antenna, the present invention may be used on only one side 15 of the case 14. However, in some cases, especially about 90
When using loop antennas at higher frequencies such as 0 MHz, resonating the antenna requires a very small capacitance to cancel the inductive reactance of the antenna. In such a case, another capacitor 40
In series with the capacitor 50, preferably on the other opposite side 17 of the case 14, to reduce the capacitance to the value required to resonate the antenna. Both sides 15, 1 of case 14
7 with a larger capacity device 11
It has been found that forming a smaller capacitor from one series capacitor (capacitor 50 and another capacitor 40) is economically preferable to using a device with a small capacitance on only one side 15 of the case. This is because the same larger capacity device could instead be used only on one side 15 of the case of another selective call receiver operating at a lower frequency.

The device 11 and the antenna 24 are designed so that small dust and dirt between the first plate 22 and the second plate 26 will not adversely affect the circuit performance. For example, at lower selective call receiver operating frequencies, a desirable value for capacitor 50 is described above in the range of 2-10 pF, but closer to 10 pF than 2 pF. Small dust or dirt between the first plate 22 and the second plate 26 does not significantly affect the capacitance value close to 10 pF and does not sacrifice the circuit performance. Although FIG. 8 shows capacitors used for impedance matching, inductors or other types of impedance matching circuitry could alternatively be used in the present invention.

While a detailed description of the preferred embodiment of the invention has been provided, it is to be understood that many variations can be made without departing from the scope of the invention as set forth in the appended claims. . For example, the angular dimension of the capacity plate attached to the case is preferably smaller than the angular dimension of the capacity plate attached to the strap, but the angular dimension of the capacity plate attached to the case is smaller than the angular dimension of the capacity plate attached to the strap. May be larger than the angular dimension of. Further, it is preferable that the capacitance plate attached to the case is concave and the capacitance plate attached to the strap is convex, but the capacitance plate on the case is convex and the capacitance plate on the strap is concave. Is also predicted. Moreover, there are many other types of antenna structures that can be used with the present invention. The device is also preferably used when the selective call receiver is worn on the wrist, but it is anticipated that the selective call receiver will be worn on another part of the human body. Further, the invention is not limited to selective call receivers, but can be used with other types of receivers and transmitters and transceivers. Further, the capacitance plate and the pin are not limited to the metal material, and may be any conductive material. Further, the material used for the case and strap is not limited to plastic. Ceramics may be used instead of plastic, especially at higher frequencies.

[Brief description of drawings]

FIG. 1 shows a device for electrically coupling an antenna to a selective call receiver in accordance with a preferred embodiment of the present invention, such as a partially disassembled view of the selective call receiver and the antenna carried by a wrist strap. FIG.

2 is an enlarged side view of a portion of the apparatus of FIG. 1 taken through line xx ′ of FIG.

FIG. 3 is a side view of the device of FIG. 1 showing the unidirectional swing limit of the strap.

FIG. 4 is a cross-sectional view of the device of FIG. 1, showing the limit of pivoting of the strap in different directions.

FIG. 5 is a partially exploded isometric view of another embodiment of an apparatus for electrically coupling an antenna to a selective call receiver in accordance with a preferred embodiment of the present invention.

6 is a top view of a portion of the apparatus of FIG.

7 is an enlarged side view of a portion of the apparatus of FIGS. 5 and 6 taken through straight line yy 'of FIG.

FIG. 8 is a simple circuit diagram showing a capacitor of the present invention and a matching circuit between an antenna and a receiver.

[Explanation of symbols]

 10 Selective Call Receiver 11 Coupling Device 12 Receiver Circuit 13 Strap Ends 14 Cases 15, 17 Opposing Sides of Case 16 Cover 18 Straps 19 and 21 Sides 20 Bow-Shaped Dimples 22, 26 Capacity Plate 23 Shaft of First Capacity Plate 24 Antenna 25 Antenna End 28 Conductor 29 Strap Hollow Cylindrical Opening Shaft 30 Strap Hollow Cylindrical Opening 31 Length of First Capacitance Plate 32 Pins 34 Pin Barrel 36, 38 Pin Extension 39, 41 cylindrical arcuate portion 44 outer surface of case 45 distance 50 capacitor 56, 57, 58, 59 mount 60, 61 cavity 62 edge of cover 64 inner corner of case

Claims (20)

[Claims] 1. A device for facilitating the wearing of a selective call receiver on a wrist, wherein the selective call receiver is supported by a case and has a strap for securing the case to the wrist. A device having the strap rotatably connected and a flexible antenna carried by the strap: a capacitor having a first plate and a second plate separated by a preselected distance. Wherein the first plate is fixed on the case and electrically coupled to the selective call receiver, and the second plate is fixed to the strap and electrically coupled to the flexible antenna. A capacitor for rotating the strap with respect to the case, the means being on the case, the first plate being Pivoting means apart; and means for maintaining said preselected distance between said first plate and said second plate during pivoting of said strap with respect to said case, said means being on said strap A maintenance means separate from the second plate. 2. The selective call receiver of claim 1, wherein the preselected distance is selected to produce a capacity having negligibly small reactance at the operating frequency of the selective call receiver. 3. The selective call receiver of claim 2, wherein the first plate forms an outer surface of the case. 4. The selective call receiver of claim 2, wherein the second plate forms an outer surface of the strap. 5. The selective call receiver of claim 1, wherein the first plate has no means for pivoting the strap with respect to the case. 6. The second plate does not have the means for maintaining the preselected distance between the first plate and the second plate during pivoting of the strap with respect to the case. The selective call receiver according to claim 1. 7. The selective call receiver of claim 1 including means for limiting the pivoting of the strap with respect to the case to a preselected degree. 8. The selective call receiver of claim 7, wherein the first plate and the second plate are cylindrical arcuate portions, the arcuate portions being less than 270 degrees. 9. The selective call receiver of claim 8, wherein the arcuate portions are of substantially different frequencies. 10. The selective call receiver of claim 9, wherein the preselected frequencies are substantially equal to different frequencies. 11. A receiver circuit; a case for gripping the receiver, the case having a pair of mounts, at least one mount being electrically coupled to the receiver circuit; At least one elongate strap for securing a case to a user, the strap having two sides and having a transverse hollow cylindrical opening having a diameter and an axis extending between the two sides; A shielded metal cylinder having a diameter greater than the diameter of the hollow cylindrical opening and coaxially embedded within said at least one elongated strap; retained by said at least one elongated strap and said shield. A metal cylindrical pin having a diameter approximately the same as the diameter of the transverse hollow cylindrical opening, , The metal cylindrical pin is removably mounted on the pair of mounts to provide the at least one
Two mounts and an electrical connection, which are coaxially removably disposed within the lateral hollow cylindrical opening and are configured to act as a capacitive metal cylindrical pin with the interrupted metal cylindrical portion; A selective call receiver characterized in that. 12. The metal cylindrical pin interacts with the interrupted metal cylindrical portion to produce a capacitance having negligible reactance at the operating frequency of the selective call receiver. Selective call receiver as described. 13. The selective call receiver of claim 11, wherein said at least one elongate strap is pivotable about a case at said transverse hollow cylindrical opening. 14. The selective call receiver of claim 13 wherein said cylindrical metal pins comprise means for pivoting around said case in said pair of mounts. 15. The metal cylindrical pin is sized to fit snugly within the lateral hollow cylindrical opening, and the at least one elongated strap and the metal cylindrical pin together without relative movement. Rotating 14.
Selective call receiver as described. 16. The selective call receiver of claim 11, wherein the shielded metallic cylindrical portion substantially surrounds the metallic cylindrical pin. 17. The selective call receiver of claim 11, wherein the case and the pair of mounts are formed of a continuous material. 18. A device for electrically coupling an antenna supported by an insulating material to a selective call receiver supported by a case, wherein the insulating material is pivotally mounted to the case by two hinges. A device comprising: a capacitor disposed between the two hinges and having a first plate on the case and a second plate on the insulating material; and the capacitor while the insulating material pivots with respect to the case. A device for maintaining the capacity of the device substantially constant. 19. Each of the two hinges has a portion on the case and another portion on the insulating material, the case and the portion of each of the two hinges being on the case. 19. Formed from a continuous material.
The described device. 20. The apparatus of claim 19, wherein the first plate forms a convex portion of the outer surface of the case and the second plate forms a concave portion of the outer surface of the insulating material.